It is presently common practice in automoblie tire plants to transport tread forming blanks on wheeled stock racks to the point where the treads are assembled on the tire carcass. The wheeled stock racks include a plurality of trays supported on upright supports for swinging movement between a generally horizontal position and a raised position. The tire treads are carried on the top of the trays and the trays have a depth sufficient to accommodate the tire tread on the subjacent tray. As treads are removed from the top of a tray, the tray is swung to a raised position to allow access to the tread forming blank on the subjacent tray. The trays must be quite long to accommodate the length of the tire tread forming blanks and, in order to maximize the number of trays in each stock rack, it is desirable to make the trays as shallow as possible consistent with providing clearance for the tread forming blank on a subjacent tray and also providing adequate strength in rigidity to prevent excessive distortion or even buckling of the tray in use.
In the applicants prior U.S. Pat. Nos. 3,680,710; 3,762,572 and 3,905,310, assigned to the assignee of the present invention, there are disclosed stock rack constructions in which the trays have a rolled rim along the rear edge of the tray to stiffen the tray and avoid sharp edges which could cause injury to the user. In the tire tray rack disclosed in the aforementioned U.S. Pat. Nos. 3,680,710 and 3,762,572, the trays were hingedly supported only at the ends of the trays by hinge pins that rotatably extended through openings in the end upright supports and non-rotatably fit in the ends of the rolled rim on the rear edge of the tray. The end upright supports provided only a narrow bearing area and the hinge pins on the trays which turned in the openings in the supports tended to wear rapidly. Moreover, because of the relatively long length of the trays required for the tire treads, there is some tendency for the trays to sag and distort due to the weight of the tire treads when the trays are supported only at their ends.
In the applicant's prior U.S. Pat. No. 3,904,310 there is disclosed a tire rack construction in which a rolled rim on the rear edge of the tray was directly supported in semi-circular recesses formed in end upright supports and in one or more intermediate upright supports. This construction swingably supported the rear edges of the trays not only at the rear ends but also at one or more intermediate locations to inhibit longitudinal buckling or distortion of the trays due to the weight of the tire treads. However, the construction shown in U.S. Pat. No. 3,905,310 required the use of open-sided recesses in the upright supports and rolled rim of the tire tray would sometimes become dislodged from the recess in the supports, particularly if the tire tray was warped or bent. In addition, the upright supports provided only a narrow bearing area which tended to concentrate the wear on the rolled rim of the tray and it was necessary to provide bearing inserts on the upright supports to reduce wear on the rolled rim of the trays.